This addon comes from Slartibartfast (nice HHGG reference, by the way). If you're just a skinner/herbalist who doesn't cook, then you'll find no use for this addon. Sorry, that's just the way things go.
What does it do right?
There are two major reasons I love this addon. a) the ability to queue complex items in engineering so that it will process its way through creating all of the little pieces so that I can create the item and b) the ability to do custom categories for things like inscription so you can separate things the way you want them. Those two things alone make this addon worth while.
Let's talk about the queue it has. When working with the addon, you can either decide to just create something or add it to the queue of things you want to make. If you're someone who has a certain list of things you keep stocked on the auction house, you can just queue up each one right after the other and then check what materials you're missing before creating the whole batch. Another part of this feature is if, for example, you're an engineer and you've finally acquired the schematic for Jeeves, you're going to need to create a whole laundry list of things in order to build him. Instead of going through and writing down on a piece of paper everything you need, just click on Jeeves and hit 'Queue' and suddenly everything needed for him is popped into the interface from the fused wiring to the cobalt bolts. After that, you can decide if you want to farm or buy your mats. For things like leatherworking or tailoring it will list something as being creatable even if you only haven't made your borean leather into heavy borean or your frostweave into bolts.
The other nice thing is that any base parts from things in your queue will show in a little box under the auction house. There is also a buy reagents button at the top of vendors so that if you need a stack of vials for all of the potions you're making, you just walk over to the vendor, hit the button, and it will buy however many you need. These settings for materials needed is shared across characters, so if you have a designated auction house or bank character you'll be able to hop over to it and still see the items you need.
Where does it need work?
One major complaint is that various tradeskills on your characters are unable to interact. If you need two titanium bars more for blacksmithing and you've got four titanium ore in your bags that you could smelt, it doesn't understand that it could convert them for blacksmithing. Part of this is probably drawbacks within the way Blizzard handles skills in that you must have the skill window up in order to create something. Also, if you accidentally queue things in the wrong order, you must delete everything out to change items at the beginning.
Overall, it's a very good addon, especially for anyone who does a lot of crafting. I've got a lot of screenshots in the gallery and more explanation of the features so go and take a look.
Where can I get it?
Available from: [Curse] [WoWInterface]